Improving the electrophilicity of nitrogen on nitrogen-doped carbon triggers oxygen reduction by introducing covalent vanadium nitride

Nitrogen-doped carbon (NC) demonstrates great promise as an alternative electrocatalyst for the oxygen reduction reaction (ORR). The C atoms next to the N dopant have been identified as the exact active sites, and optimizing the electronic structure of N has a great effect on the activity. In this study, a novel VN@NC nanocomposite consisting of a vanadium nitride (VN) nanoparticle core and chainmail-like NC shell has been constructed via a simple physical mixing and annealing process. Benefiting from the unique core@shell nanowire structure and modulated electronic structure, the as-prepared VN@NC manifests an obviously promoted ORR activity (onset potential: 0.93 V) compared with pure NC and bulk VN. Specifically, incorporating VN induces charge transfer from N on NC to V in VN and increases the electrophilicity of N on NC, resulting in optimized adsorption to O-containing intermediates. VN@NC also manifests decent long-term stability (89% current density retention after a 40,000-s test). This finding highlights the significance of regulating the electronic structure of N in NC and provides a reliable strategy for constructing NC-based hybrid electrocatalysts.